While I like using powder horns, for muzzleloader hunting, I find pre-measured charges of powder and shot put up in nickel wrappers works better. I get fistfuls of nickel wrappers free at my bank. I turn back about a quarter inch of one end, scotch tape it fast, insert the powder or shot and tape the other end. I put the wrappers in a baggie and drop it into the possibles bag. Afield, I pull out a wrapper of powder, tear it open, pour the charge and load the projectile. If a wrapper is dropped afield, it is biodegradable.

My civil war reenactment unit makes up blanks for our M1853 caliber .577 Enfields by putting 75 grains of 2F Goex in nickel wrappers. We just pour the charge down the barrel, cap and fire.